1. Technical Field
This invention relates generally to integrated lead suspension assembly for a data recording disk drive and more particularly to a flexure which connects a transducer to a load beam within an integrated suspension, which is capable of vertical and angular deformation to effect a desired mechanical and electrical connection between the integrated suspension leads and the transducer.
2. Description of the Prior Art
Direct access storage devices (DASD), such as disk drives, store information on concentric tracks of a rotatable magnetic recording disk. In order to read or record the desired information on a rotating disk, a magnetic head or other transducer element on a suspension arm is moved from track to track by a rotary or linear actuator. The suspension arm is part of a head suspension assembly that typically includes a load beam attached to an actuator arm, a flexible member known as a flexure connected to the load beam, and a transducer or magnetic head attached to the flexure. The magnetic heads, which actually read or write data on the disk, are positioned within an air bearing slider. While the disk rotates, the slider flies slightly above the surface of the rotating disk, the load beam supports the slider and the flexure allows it to gimbal to adjust its orientation for unavoidable disk surface run out or flatness variations. The combination flexure/transducer are often referred to as the head gimbal assembly.
Examples of suspension systems are shown in the following references: U.S. Pat. No. 5,491,597 to Bennin et al. issued Feb. 13, 1996; U.S. Pat. No. 5,490,027 to Hamilton et al., issued Feb. 16, 1996; U.S. Pat. No. 5,428,489 to Takamure et al., issued Jun. 27, 1995; U.S. Pat. No. 5,377,064 to Yaginuma et al., issued Dec. 27, 1994; U.S. Pat. No. 5,282,102 to Christianson, issued Jan. 25, 1994; U.S. Pat. No. 5,225,950 to Crane, issued Jul. 6, 1993; U.S. Pat. No. 5,198,945 to Blaeser et al., issued Mar. 30, 1993; U.S. Pat. No. 5,187,625 to Blaeser et al., issued Feb. 16, 1993; U.S. Pat. No. 5,115,363 to Khan et al., issued May 19, 1992; U.S. Pat. No. 4,996,623 to Erpelding et al., issued Feb. 26, 1991; U.S. Pat. No. 4,797,763 to Levy et al., issued Jan. 10, 1989; U.S. Pat. No. 4,761,699 to Ainslie et al., issued Aug. 2, 1988. European Patent Application Publication No. 0487914A2 to Foote et al., published Jun. 3, 1992; PCT Publication No. WO94/24664 for Jurgenson, published Oct. 27, 1994; PCT Publication No. WO 94/16438 for Budde, published Jul. 21, 1994; PCT Publication No. WO 94/12974 for Budde, published Jun. 9, 1994 and Japanese Patent Publication No. 59-207065 for Hashimoto, published Nov. 24, 1984.
As indicated by the prior art, in a conventional air-bearing slider-suspension assembly, the slider is mechanically attached to the flexure element of the suspension by epoxy bonding. The electrical connection between the transducer and the read/write electronics is made of twisted wires which run the length of the suspension load beam and extend over the flexure element and the slider. The ends of the wires are soldered or ultrasonically bonded to the transducer bonding areas or pads located on the slider. Another type of suspension is a composite or laminate structure with patterned electrical leads formed thereon. In the laminated suspensions, the slider is epoxy bonded to the laminated suspension and the transducer leads are formed on the suspension. Assignee's U.S. Pat. No. 4,761,699 describes a laminated suspension for use with a conventional slider wherein solder ball connections provide both the mechanical connection of the slider to the laminated suspension and the electrical connection of the transducer to the leads on the laminated suspension.
It is well known that a head gimbal assembly must provide a proper pivotal connection for the slider so that during operation, the slider can compensate for irregularities in manufacture and operation by pitching and/or rolling slightly in order to maintain the air bearing, while maintaining appropriate stiffness against yaw movement. Roll is defined as rotation about a longitudinal axis extending directly out from the actuator arm in the plane of the disk, and pitch is defined as rotation about an axis perpendicular to the roll axis but still lying in the plane of the disk. Yaw is gyration around an axis perpendicular to the air-bearing surface. In order to be useful, any flexure must achieve low enough pitch and roll stiffness for the air bearing flying height tolerances while at the same time achieving high enough yaw stiffness.
Another important consideration for a head gimbal assembly is that it must provide good dynamic characteristics. When the suspension is being actuated to seek a track or when it is being excited by external forces such as air flow, certain modes of vibration of the flexure can be excited. The mode of vibration of concern is the flexure leg out of phase bending mode. If this mode of vibration is excited, the suspension will exhibit large gain in the sway direction. Therefore, it is desirable to place this mode of vibration high in the frequency range to avoid any servo problem.
One of the problems associated with disk drives using a conductive base conventional suspension or laminated type suspension is the creation of a vertical displacement in a portion of the bonding area to which the slider is bonded by virtue of an insulating layer applied to suspension. An insulating layer is needed to prevent the magnetic head from being shorted when the slider bonding pads are bonded to the electrical leads or wires on the suspension. This vertical displacement defines a gap between the slider back surface and the flexure, which is encountered when attempting to bond the flexure to the slider.
There are several problems encountered as the result of this vertical displacement in the slider bonding area. For instance, when the slider is bonded to the flexure, the flexure tongue has to be flat with respect to the slider's back surface. If the distortion on the flexure tongue due to the vertical deflection is too excessive, the slider cannot be bonded securely to the flexure. During manufacturing, the slider is usually being held in a tool block when it is being bonded to the flexure. The suspension with the integrated flexure is then pressed down onto the slider. Part of the flexure will have to deflect a small amount in the vertical direction so that the back of the slider and the flexure tongue will be back to back for bonding. However, in doing so, internal forces and moments are created. Furthermore, after the slider is bonded, the epoxy is cured, and the suspension is taken out of the tool block, the internal forces and moments will rotate the flexure and bias the pitch and static attitude of the suspension.
Another drawback encountered in the prior art approach is that the amount of force available for bonding the slider to the flexure is the gram load of the suspension load beam. The tip of the flexure has to be compliant enough to be deformed vertically using no more than this amount of force. The smaller the amount of force is required for this deformation, the less resulting distortion and static attitude bias on the flexure.
Yet another disadvantage encountered as a result of the vertical displacement in the bonding area is the problem of tilting. It is known that when the tip of the flexure is displaced vertically, it will also tilt. This tilting is undesirable for several reasons. The tip of the flexure is a platform for slider read/write element terminations. The edge of the slider which contains the read/write elements and the flexure platform should ideally be perpendicular to each other. Any amount out of perpendicular will increase the termination tolerance. In addition, for a low profile suspension, the distance between the suspension load beam and the flexure is small. Any tilting at the tip of the flexure will decrease that small distance further and increase the chance of interference.
It therefore would be an advantage to provide an integrated suspension assembly wherein the flexure provides adequate support for the air-bearing slider while being compliant with the layers of the integrated suspension assembly. It would also be advantageous to provide a means to increase the frequency of the flexure leg out of phase bending mode of vibration without increasing the low pitch and roll stiffness required for flying height tolerance and at the same time increasing yaw stiffness.